A lever apparatus is widely used in the field of machinery, such as machine tools and industrial machines, and in the power transmission portions of moving mechanisms of structures of various types. FIGS. 1 and 2 show examples of a power transmission mechanism that utilizes the principles of a lever.
In the example shown in FIG. 1, pin links 13 and 14 are provided for the circumferential portions of a disk 12 rotatable with a stationary fulcrum as a center, such that the pin links 13 and 14 are apart from each other by 90.degree.. The pin link 13 serving as a force point is coupled, through a coupling member 15a extending in a tangential direction of the disk 12, to one end of a driving arm 17 supported by a support shaft 16. The other end of the driving arm 17 is coupled through a driving link 18 to a driving section. The pin link 14 serving as an action point is coupled, through a coupling member 19a extending in a tangential direction of the disk 12, to the tip end of a driven section 22 of a hydraulic device 21 supported by a support shaft 20.
In the example shown in FIG. 1, the linear motion of the driving link 18 rotates the driving arm 17, and power is transmitted through the coupling member 15a to the disk 12 (i.e., a lever apparatus) and is further transmitted through the coupling member 19a to the hydraulic device 21. However, the pin links 13 and 14, respectively serving as a force point and an action point, describe an arc when the disk 12 is rotated. Thererover each of the coupling members 15a and 19a does not linearly reciprocate but swings widthwise. In other words, the linear driving force of the driving link 18 cannot be transmitted to the coupling member 19 as a linear operating force.
In the example shown in FIG. 2, where a fulcrum 23 is fixed and a force point 24 is lowered, an action point roller 25 is strained in such a manner as to bend a coupling member 19b in the indicated direction. When this type of device is used for a long time, those portions of a guide 26 which are depicted as being upper left and lower right portions with reference to a guide hole are likely to be abraded.